1. The Field of the Invention
This invention relates to ladders and, more particularly, to novel structures, systems, and methods for lightweight ladders.
2. The Background Art
Ladders are convenient for providing a user with access to locations that would otherwise be inaccessible. Ladders are typically available in several configurations, namely straight ladders, straight extension ladders, step ladders, and combination step and straight extension ladders (“combination ladders”). Each type of ladder may have particular situations for which it is best suited. Combination ladders are particularly useful because they provide, in a single ladder, most of the benefits of the other ladder designs. However, typical combination ladders are hampered by excessive weight, higher purchase costs, and safety concerns raised by the increased complexity of the ladder design.
In contrast to simpler ladder designs, combination ladders must support multiple load configurations. As a result, the structural elements of the ladder must be reinforced to support the loads. For example, the hinge of a combination ladder in a straight configuration must withstand larger moment loads than the hinge of a step ladder. Additionally, the hinge of a combination ladder must rigidly support the upper half of the ladder above the lower half. These load and rigidity requirements of a combination ladder hinge result in thicker components and more reinforcement material, both of which contribute to additional weight of the ladder.
Additionally, combination ladders are more expensive than traditional ladder designs. As stated above, combination ladders require additional reinforcement to compensate for the various loadings that may be applied. Stronger materials or simply additional materials increase the cost of the ladder. The greater complexity of combination ladders also increases assembly costs.
Furthermore, combination ladders present additional safety concerns. Due to the fact that combination ladders are by design collapsible, inadvertent release of the hinge may result in a total collapse of the ladder. For example, a hinge may contain a selective locking and releasing mechanism for maintaining the hinge in certain selected positions. A worker, through inadvertence or mistake, or even through stumbling or other physical imbalance, may, in some circumstances, strike a release mechanism, endangering the rigidity of the locking mechanism holding a hinge in a specific position. Typical combination ladders do not provide a remedy for such potential hazards.
Accordingly, what is needed is a combination ladder with components designed and arranged to provide the maximum strength without significantly increasing the over all weight of the ladder. Additionally, ladder components need to be designed to promote ease of manufacture and assembly, thus reducing the cost of the combination ladder. Moreover, what is needed is additional safety features such as an interlock that requires affirmative, intentional actions on behalf of a user, before a release mechanism actuates. It would be an advance in the art if the interlock and the release mechanism could both be operated by a single hand of a single user, simultaneously, but only intentionally.